1. Field of the Invention
The present invention relates to an image sensing apparatus and, more particularly, to a method of combining a character pattern with a video signal obtained by image sensing.
2. Description of the Related Art
In the NTSC system which is one existing standard television system, the aspect ratio, i.e., the ratio of the frame width and the frame height of a screen, is 4:3. As a matter of course, imaging apparatus such as cameras and displays are designed on the assumption that the aspect ratio is 4:3.
In such a situation, an ED-TV (extended definition TV) broadcasting system having an aspect ratio of, for example, 16:9 which is wider than the existing aspect ratio has recently been considered in order to provide a television broadcast which is improved in image quality and presence. If the ED.TV broadcasting system is practiced, there will be provided imaging apparatus such as cameras and displays which adopt wider screens while basically conforming to an existing television system such as the NTSC system.
FIGS. 6 to 8 illustrate various images which are reproduced on a display from an image photographed by a conventional video camera.
In FIG. 6, a subject 20 has a size which can be completely viewed through an optical system having the angular field of view equivalent to the 16:9 aspect ratio, and a video camera 21 is of an existing type which employs an image sensing system having an aspect ratio of 4:3.
Conventionally, the video camera 21 is provided with the function of superimposing information such as a title on a sensed image on a screen by combining character information with image information obtained by image sensing, and recording the superimposed information such as a title together with the sensed image.
In FIG. 6, each of display examples (a) to (d) shows a different, specific displayed image in which a title or a display of the time of photography is combined with a photographed image.
In the case of an existing type of display (4:3 aspect ratio), a visual display is provided like the display example (a) or (b) shown in FIG. 6.
In the case of a wide display (16:9 aspect ratio), areas free of a signal appear on both ends of the screen, but combined character information is correctly displayed, as shown by each of the display examples (c) and (d) of FIG. 6.
The state of an image which is reproduced on a display screen when an image sensed through an anamorphic lens is displayed on a display will be described below with reference to FIG. 7.
In FIG. 7, the same reference numerals are used to denote portions which are substantially identical to or correspond to those shown in FIG. 1, and the description thereof is omitted.
In FIG. 7, a linear compression optical system (anamorphic lens) 22 is detachably attachable to the video camera 21.
The video camera 21 is capable of varying the aspect ratio of a photographed image by compressing the photographed image by means of the anamorphic lens 22, and forming an image of wide aspect ratio by image sensing.
When the thus-sensed image is to be reproduced on a display, expansion processing reverse to the compression processing performed during the photography is carried out.
If such a sensed image is reproduced on a display having a screen of wide aspect ratio, an image without any problem is displayed like the display example (c) shown in FIG. 7, and the subject 20 is faithfully reproduced.
If the image sensed by the video camera 21 is reproduced on a display having the existing 4:3 aspect ratio, a vertically elongated image which has been compressed to 3/4 along its frame width is reproduced on the display. As a result, a distorted image like the display example (a) of FIG. 7 will be reproduced.
To cope with the above-described problem, it is proposed to adopt a display method including the steps of applying expansion processing to an image during reproduction in a manner similar to the manner in which a visual display is provided on the display having a screen of wide aspect ratio, cutting both sides from the image and displaying the image in such a manner that it is accommodated within a screen having the 4:3 aspect ratio (refer to the display example (b) of FIG. 7).
However, the display method of providing a visual display like the display example (b) of FIG. 7 has a number of problems. For example, if information, such as the date or time of photography, is combined with a sensed image, the information is usually located at a corner of the screen. As a result, an image devoid of such information will be reproduced on the screen of a display, as shown by the display example (d) of FIG. 8, and it will be impossible to confirm, for example, the time of photography.
As described previously, conventionally, the video camera 21 is provided with the function of superimposing information such as a title on a sensed image on a screen by combining character information with image information, and recording the superimposed information together with the sensed image.
However, if an image of wide aspect ratio is photographed with an existing type of camera using the above-described anamorphic lens and is recorded by means of the aforesaid function, the following problem will occur. If an image which has not been subjected to expansion processing is displayed on a display of standard aspect ratio, an image like the display example (a) of FIG. 8 will be displayed, that is, the title is displayed without distortion, but the photographed image is distorted.
If such a photographed image is subjected to expansion processing and displayed on a display of standard or wide aspect ratio, the photographed image will be displayed without distortion.
However, since title information which has been combined with the image is also expanded during the expansion processing, the character information shown as a display example (g) in FIG. 8 is displayed on the screen in a horizontally expanded shape during reproduction. As a result, the shapes of individual characters indicative of the title information differ from those of the original characters used during the combination (refer to display examples (b) and (e) in FIG. 8).